Browning Robert, Plachinda Paul, Padigi Prasanna, Solanki Raj, Rouvimov Sergei
Department of Physics, Portland State University, Portland, OR, USA.
Department of Electrical Engineering, University of Notre Dame, Notre Dame, IN, USA.
Nanoscale. 2016 Jan 28;8(4):2143-8. doi: 10.1039/c5nr08006a.
Both WS2 and SnS are 2-dimensional, van der Waals semiconductors, but with different crystal structures. Heteroepitaxy of these materials was investigated by growing 3 alternating layers of each of these materials using atomic layer deposition on 5 cm × 5 cm substrates. Initially, WS2 and SnS films were grown and characterized separately. Back-gated transistors of WS2 displayed n-type behavior with an effective mobility of 12 cm(2) V(-1) s(-1), whereas SnS transistors showed a p-type conductivity with a hole mobility of 818 cm(2) V(-1) s(-1). All mobility measurements were performed at room temperature. As expected, the heterostructure displayed an ambipolar behavior with a slightly higher electron mobility than that of WS2 transistors, but with a significantly reduced hole mobility. The reason for this drop can be explained with transmission electron micrographs that show the striation direction of the SnS layers is perpendicular to that of the WS2 with a 15 degree twist, hence the holes have to pass through van der Waals layers that results in drop of their mobility.
WS2和SnS都是二维范德华半导体，但具有不同的晶体结构。通过使用原子层沉积在5 cm×5 cm的衬底上生长这两种材料的各3个交替层，对这些材料的异质外延进行了研究。最初，分别生长并表征了WS2和SnS薄膜。WS2的背栅晶体管表现出n型行为，有效迁移率为12 cm² V⁻¹ s⁻¹，而SnS晶体管表现出p型导电性，空穴迁移率为818 cm² V⁻¹ s⁻¹。所有迁移率测量均在室温下进行。正如预期的那样，异质结构表现出双极性行为，电子迁移率略高于WS2晶体管，但空穴迁移率显著降低。这种下降的原因可以用透射电子显微镜照片来解释，照片显示SnS层的条纹方向与WS2的条纹方向垂直且有15度的扭曲，因此空穴必须穿过范德华层，这导致它们的迁移率下降。
